mirror of
https://github.com/bsnes-emu/bsnes.git
synced 2025-02-23 14:42:33 +01:00
byuu says: - bsnes: added video filters from bsnes v082 - bsnes: added ZSNES snow effect option when games paused or unloaded (no, I'm not joking) - bsnes: added 7-zip support (LZMA 19.00 SDK) [Recent higan WIPs have also mentioned bsnes changes, although the higan code no longer includes the bsnes code. These changes include: - higan, bsnes: added EXLOROM, EXLOROM-RAM, EXHIROM mappings - higan, bsnes: focus the viewport after leaving fullscreen exclusive mode - bsnes: re-added mightymo's cheat code database - bsnes: improved make install rules for the game and cheat code databases - bsnes: delayed construction of hiro::Window objects to properly show bsnes window icons - Ed.]
129 lines
3.6 KiB
C++
129 lines
3.6 KiB
C++
#pragma once
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//reed-solomon product code
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namespace nall::CD::RSPC {
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inline auto encodeP(array_view<uint8_t> input, array_span<uint8_t> parity) -> bool {
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ReedSolomon<26,24> s;
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uint lo = 0, hi = 43 * 2;
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for(uint x : range(43)) {
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for(uint w : range(2)) { //16-bit words
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uint z = 0;
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for(uint y : range(24)) {
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s[z++] = input[(y * 43 + x) * 2 + w];
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}
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s.generateParity();
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parity[lo++] = s[z++];
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parity[hi++] = s[z++];
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}
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}
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return true;
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}
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inline auto encodeQ(array_view<uint8_t> input, array_span<uint8_t> parity) -> bool {
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ReedSolomon<45,43> s;
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uint lo = 0, hi = 26 * 2;
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for(uint y : range(26)) {
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for(uint w : range(2)) {
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uint z = 0;
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for(uint x : range(43)) {
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s[z++] = input[((x * 44 + y * 43) * 2 + w) % (26 * 43 * 2)];
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}
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s.generateParity();
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parity[lo++] = s[z++];
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parity[hi++] = s[z++];
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}
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}
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return true;
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}
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inline auto encodeMode1(array_span<uint8_t> sector) -> bool {
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if(sector.size() != 2352) return false;
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if(!encodeP({sector + 12, 2064}, {sector + 2076, 172})) return false;
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if(!encodeQ({sector + 12, 2236}, {sector + 2248, 104})) return false;
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return true;
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}
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//
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inline auto decodeP(array_span<uint8_t> input, array_span<uint8_t> parity) -> int {
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bool success = false;
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bool failure = false;
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ReedSolomon<26,24> s;
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uint lo = 0, hi = 43 * 2;
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for(uint x : range(43)) {
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for(uint w : range(2)) {
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uint z = 0;
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for(uint y : range(24)) {
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s[z++] = input[(y * 43 + x) * 2 + w];
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}
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s[z++] = parity[lo++];
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s[z++] = parity[hi++];
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auto count = s.correctErrors();
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if(count < 0) {
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failure = true;
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}
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if(count > 0) {
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success = true;
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z = 0;
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for(uint y : range(24)) {
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input[(y * 43 + x) * 2 + w] = s[z++];
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}
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parity[lo - 1] = s[z++];
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parity[hi - 1] = s[z++];
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}
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}
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}
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if(!success && !failure) return 0; //no errors remaining
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return success ? 1 : -1; //return success even if there are some failures
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}
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inline auto decodeQ(array_span<uint8_t> input, array_span<uint8_t> parity) -> int {
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bool success = false;
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bool failure = false;
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ReedSolomon<45,43> s;
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uint lo = 0, hi = 26 * 2;
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for(uint y : range(26)) {
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for(uint w : range(2)) {
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uint z = 0;
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for(uint x : range(43)) {
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s[z++] = input[((x * 44 + y * 43) * 2 + w) % (26 * 43 * 2)];
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}
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s[z++] = parity[lo++];
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s[z++] = parity[hi++];
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auto count = s.correctErrors();
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if(count < 0) {
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failure = true;
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}
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if(count > 0) {
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success = true;
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z = 0;
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for(uint x : range(43)) {
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input[((x * 44 + y * 43) * 2 + w) % (26 * 43 * 2)] = s[z++];
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}
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parity[lo - 1] = s[z++];
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parity[hi - 1] = s[z++];
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}
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}
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}
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if(!success && !failure) return 0;
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return success ? 1 : -1;
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}
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inline auto decodeMode1(array_span<uint8_t> sector) -> bool {
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if(sector.size() != 2352) return false;
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//P corrections can allow Q corrections that previously failed to succeed, and vice versa.
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//the more iterations, the more chances to correct errors, but the more computationally expensive it is.
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//there must be a limit on the amount of retries, or this function may get stuck in an infinite loop.
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for(uint attempt : range(4)) {
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auto p = decodeP({sector + 12, 2064}, {sector + 2076, 172});
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auto q = decodeQ({sector + 12, 2236}, {sector + 2248, 104});
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if(p == 0 && q == 0) return true; //no errors remaining
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if(p < 0 && q < 0) return false; //no more errors correctable
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}
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return false; //exhausted all retries with errors remaining
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}
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}
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